It has become popular in some circles to say that sanctification is really about getting used to the verdict that we have in justification. While this is an important aspect of my sanctification and I agree that sanctification is gospel-centered, this is not typically the Reformed, and I would argue Biblical, approach to sanctification.
In the book "Christian Spirituality: Five Views on Sanctification," Gerharde O. Forde, writing for the Lutheran view, states:
"But is there not such a thing as growth in sanctification, progress in the Christian life? No doubt there is a sense in which we can and even should speak in such a fashion. But when we do, we must take care, if everything we have been saying up to this point is true. If justification by faith alone rejects all ordinary schemes of progress and renders us simultaneously just and sinners, we have to look at growth and progress in quite a different light.
That brings us back to our thesis: sanctification is the are of getting used to justification. There is a kind og growth and progress, it is to be hoped, but it is growth in grace--a growth in coming to be captivated more and more, if we can so speak, by the totality, the unconditionality of the grace of God. It is a matter of getting used to the fact that if we are to be saved it will be by grace alone. We should make no mistake about it: sin is to be conquered and expelled. But if we see that sin is the total state of standing against the unconditional grace and goodness of God, if sin is our very incredulity, unbelief, our insistence on falling back on our self and maintaining control, then it is only through the total grace of God that sin comes under attack, and only through faith in that total grace that sin is defeated. To repeat: sin is not defeated by a repair job, but by dying and being raised new. (pp.27-28)"
There is much to commend in this extended quote. For example:
(1) We should ourselves, even in sanctification, as dependent upon grace. Salvation is all of grace or it is not at all.
(2) We should see the importance of dying to sin and rising to new life in Christ. (as we will argue in a minute this is central to union with Christ).
(3) For some, sanctification is wrongly perceived as our work for God. That tends to minimize the gravity and offensiveness of sin, create 'performance mode' Christians and reduce the reality of indwelling sin in a Christian.
Yet, this statement is insufficient because it does not make union with Christ central to our sanctification. The tendency then is to prioritize justification by faith (admittedly no small part of our redemption and salvation) but with an effect that sanctification is sort of a subsidiary effect--a left over crater if you will. So that the more I am thankful for the first part, the more the second will develop. And yet--'dying and being raised' in Paul's language especially in Romans 6 is more than merely 'my justification' (I say 'merely' not to in any way minimize justification by faith). Rather Paul's approach makes my dying and rising with Christ a functional outworking of my union with Christ.
Sinclair Ferguson responds to the above 'Lutheran' approach by highlighting three points:
"1. I have the impression from the essay that so central is the idea of justification to Lutheran thought that is not only dominates sanctification, but at times even seems to threaten to displace the person of Christ from center stage. Justification is in Christ, and is to be sought in him, not in itself. In Reformed theology (and, I believe, in Scripture) this is a motif which is fundamental to justification." (p.34).
"2. Reformed theology is as anxious as Lutheran thought to safeguard grace. It has wrestled very seriously with the whole question of conditions. The term conditions has a certain infelicity about it. But there is a difference between what we might call "conditionality" (which compromises grace by saying, "God will be gracious only if you do X or Y") and the fact that there are conditions for salvation which arise directly out of the gospel message and do not compromise its graciousness...There is a sine qua non to forgiveness and to justification. They cannot be received apart from faith. This is a biblical condition that does not compromise grace, but arises from it. The important thing is not to deny condition, but to underscore that "It is not faith that saves, but Christ that saves through faith" (B.B. Warfield)." (p.34-35)
"3. Developing this point a little further, Lutheranism has a deep reluctance to highlight the so-called 'third use of the law' (as a rule for life). I appreciate Dr. Forde's concern to avoid a legalism that defines sanctification in formal terms.
In contrast, however, Reformed teaching speaks of "the grace of the law." It recognizes the reappearance of the Decalogue in the New Testament's very concrete imperatives arising out of the gracious indicatives of the gospel... This, Reformed theology argues, was the original context of the Decalogue itself...Obedience is nothing if it is not concrete and specific. Sanctification, ultimately Christlikeness, has a definite form and structure in the New Testament, as well as a foundation and motivation in grace. This is no wise detracts from the concern both Dr. Forde and Reformed theology share in stressing that sanctification is ultimately a true humanity, because it is ultimately likeness to our Lord Jesus Christ." (p.35)
On the Reformed approach as a whole:
"Reformed Theology sees the central role of justification as does Lutheran theology. It is the 'main hinge on which religion turns' says Calvin; 'the pivotal point around which everything moves' (Geerhardus Vos). But this justification is ours only through our union with Christ. This union is also the mainspring of our sanctification: Christ is both our righteousness (justification) and our sanctification (1 Cor. 1:30 RSV)." (p34).
The following is especially golden:
"When the doctrine of union with Christ is made the architectonic principle of the application of redemption (as it was in Calvin's thought [see Institutes 2.16.19], by contrast, I believe with Luther), the tension which Lutheranism seems to feel between justification and the Christian's good works, or sanctification, begins to vanish. The one does not exist without the other, since both are effects of union with Christ. Yet neither is reduced to the other. Justification is not disgraced as though it were based upon sanctification; sanctification is not demoted, as though it were a threat to the grace of justification." p.34).
In the book Christian Spirituality: Five Views on Sanctification, the parts between the Reformed and Lutheran view are a model of how irenic but important debate can take place between confessional traditions on important issues. In his chapter, Ferguson expounds more of the Reformed view, handles Romans 6 and illustrates the centrality of union with Christ to sanctification. It is worth reading. Reading Forde's response is equally helpful for exposing potential weaknesses to the Reformed view (although I think these can be sufficiently countered).
The point of this post is again: it is becoming popular in some circles, especially some of the 'young, restless and Reformed,' to make sanctification essentially a 'getting used to the justification that I have.' While an important element because we certainly do not want to be legalists, sanctification entails more than this. Sanctification is not the cart pulled by justification and if I can just understand the strength of the horse, the cart takes care of itself. Instead we should see that both flow out of union with Christ.
Here's a video by Professor Lane Tipton on this issue: